code: def test_empty_string(self):
      primitive_func = self.primitive().get_function()
      array_empty_string = pd.concat(
          [self.array.copy(), pd.Series([np.nan, "", ""])]
      )
      assert primitive_func(array_empty_string) == (9 / 13.0)
  
file_path: featuretools/featuretools/tests/primitive_tests/transform_primitive_tests/test_percent_unique.py
imports: import numpy
  import pandas
  from featuretools.primitives import PercentUnique
  from featuretools.tests.primitive_tests.utils import PrimitiveTestBase
label_desc: Use image node_id 4 for calling the TestPercentUnique obj's underlying member method code with example usage: obj.test_empty_string() without return types